It is of importance to increase the efficiency of operations on multiple workpieces which are similar to or different from each other, and are clamped on a tooling fixture. Such workpieces can be made in small, intermediate or large series in computer numerically controlled (CNC) work centers, or can be worked on with multi-spindle machines.
Auxiliary or lateral time periods associated with the efficiency of operations on multiple workpieces include the time required for supplying the workpieces, clamping them, re-clamping them in a different position if necessary, and removing the workpieces. These auxiliary time periods form a cost factor which becomes increasingly important as the initial preparation of the workpieces themselves becomes more accurate, thus requiring little re-working.
The operations performed on multiple workpieces generally require a high degree of accuracy. Any minor inaccuracy may be compounded when performing operations on multiple workpieces. Such inaccuracies may include the position of multiple workpieces that may be secured in a multiple workpiece clamping device.
One such device is illustrated in U.S. Pat. No. 6,185,802 to Gruber et al. The device described in Gruber et al. rotates a plurality of workpieces using a combination of three gears. Unfortunately, such a gear drive arrangement may suffer from inaccuracies in positioning.
U.S. Pat. No. 4,860,414 to Bishop et al. discloses an indexing and transporting device including a plurality of workpiece spindles spaced on a carousel. The spindles are indexed together using four-lobe geneva wheels and geneva drive pins incorporated in gears which, in turn, are driven through idlers from a gear mounted on a drive shaft. Again, the spindle drive arrangement may also produce inaccuracies. Also, re-clamping the workpieces in a different position is further time-consuming, and introduces the possibility of errors in the positions of the workpieces after re-clamping.